Three-dimensional (3D) screen printing is widely used in various industries, e.g., for printing on rounded containers such as bottles and cans. 3D screen printing as yet is generally limited to substrates with a smaller radius of curvature (e.g., less than about 500 mm) and/or a single axis of curvature. For the most part, 3D printing is also limited to printing on the outside, or convex, surface of semi-circular or parabolic substrates and cylindrical substrates with circular or oval cross-sections. These substrates can typically comprise glass (e.g., bottles, mugs, glasses, etc.), plastic (e.g., containers, etc.), and/or metal (e.g., cans, castings, etc.).
The ability to screen print on larger format, larger radius, and/or multiple radius three-dimensional substrates is increasingly relevant to various industries, such as the automotive industry. Larger format 3D substrates conventionally can be printed while the substrate is still flat, followed by shaping of the substrate to achieve a 3D shape, e.g., by softening a glass or plastic substrate at elevated temperatures, or the like. However, because the printing medium can be thermally incompatible with the conditions necessary to shape the substrate after printing, there is a growing need to print on curved surfaces of large format 3D substrates. This is particularly true in the case of glass substrates, which can be heated to relatively high forming or softening temperatures during the shaping process.
Current methods for decorating the surfaces of a 3D substrate include masking a portion of the surface and spray coating the substrate to create an image; however, such methods can be costly and/or time consuming and generally do not provide a suitable image resolution. Screen printing and inkjet printing on large format curved surfaces have been attempted, but with various drawbacks, complications, and/or limitations. For instance, 3D printing devices typically comprise one or more extra moving parts as compared to 2D printing devices for purposes of maintaining an “off-contact” distance, or gap, between the substrate and the screen mesh. 2D flat screen printing processes generally maintain a constant off-contact distance ranging from about 1 to about 10 mm, depending on the printing application. 3D printing devices conventionally compensate for off-contact variability by articulating the substrate under the screen or articulating the screen above or around a fixed substrate.
Screen frames with flexible sides can also be used, such that the frame and mesh can conform somewhat to the contour of the curved substrate during printing. Screen frames pre-shaped to match the curvature of a given substrate can also be used. Devices used to tension and de-tension the screen mesh can also be attached to a screen frame to allow the mesh to conform or flex during the printing process. However, these additional components and/or features of the screen frame and/or printing machine can add to the complexity and/or expense of the 3D printing process, as the printing machines and/or their individual components often have to be custom tailored to achieve each desired feature. Moreover, such 3D screen printing methods can be used only for convex or concave surface printing, not both, and only for substrates with a single radius of curvature.
Accordingly, it would be advantageous to provide methods and apparatuses for screen printing 3D substrates, which can operate with fewer moving parts, at lower cost, and/or with lower complexity. It would additionally be advantageous to provide methods and apparatuses for printing on a variety of substrate shapes, such as concave and/or convex substrates, and/or substrates with a complex curvature, e.g., curvature around plural radii. Furthermore, to reduce manufacturing costs and/or the need to custom make the printing device and/or its components, it may be advantageous to provide an apparatus that can function, at least in part, in conjunction with existing components for printing traditional (e.g., 2D) substrates.